Cancer: How unexpected weight loss can sometimes be an indicator

Experts say rapid, unexpected weight loss can be a sign of cancer as well as other health issues. OLEKSANDRA TROIAN/Getty Images

In a new study, researchers report that health professionals who lost weight without starting a diet or exercise plan within the previous two years had a significantly higher risk of developing cancer within the following year.
Upper gastrointestinal tract, hematologic, colorectal, and lung cancers were more common in people with rapid unexpected weight loss.
Experts say people with an unexplained or unexpected weight loss of 5% or more of their body weight should see their primary care doctor.

Health professionals who had unexpected weight loss in the previous two years had a significantly higher risk of developing cancer during the subsequent 12 months compared to those who did not have recent weight loss, according to a new study published in the journal JAMA Network.

Unintentional weight loss is losing weight without changing your diet or beginning an exercise program. The study looked at a 10% or greater weight loss in the healthcare professionals.

Researchers analyzed data from the Nurse’s Health Study and the Health Professional’s Follow-Up Study to identify recent weight loss with a subsequent cancer risk. There were 157,474 participants with a median age of 62.

The scientists noted that previous studies showed an association between weight loss and a cancer diagnosis.

Cancers associated with rapid weight loss

Of the cancers associated with recent weight loss, researchers reported that upper gastrointestinal tract cancer was the most common.

Other types of cancer, including hematologic, colorectal, and lung cancers, were also found to be more common in those who had recently experienced unintentional weight loss.

The risk of cancer was higher during the first 12 months after weight loss compared to 24 months afterward.

Breast, genital, urinary, and brain cancers as well as melanoma were not associated with weight loss.

“Unexplained weight loss has always been a warning sign of a possible underlying condition,” said Dr. Wael Harb, a hematologist and medical oncologist at MemorialCare Cancer Institute at Orange Coast and Saddleback Medical Centers in California who was not involved in the research. “This study emphasizes information we already knew.”

“An unexplained loss of 5% of your body weight in six months is concerning,” Harb told Medical News Today. “People who have unexplained weight loss should start with their family physician. Other symptoms can help to narrow down where to look. Weight loss can signal a digestive disease, such as celiac or problems with thyroid. But, as the study points out, it can also signal cancer. If other illnesses are ruled out, the doctor should investigate further.”

“If cancer is missed, the doctor and patient have lost the chance to diagnose and treat early, which is important in all cancers,” Harb added.

Previous research on weight loss and cancer

This study backs up data from a previous study in 2022 that also found unexpected weight loss to be a potential sign of cancer.

The researchers concluded that the interval of when the weight loss occurred should not be considered a factor. The percentage of body weight and the person’s age are more critical factors.

Researchers for this study found an increase in pancreatic, myeloma, gastro-oesophageal, colorectal, and breast cancers as well as stage II and IV cancers after unexplained weight loss of more than 5% of body weight.

The current study found similar results.

Researchers reported that weight loss of more than 10% resulted in an increased rate of upper gastrointestinal tract, hematological, colorectal, and lung cancer. The scientists did not find some of these cancers until at least two years after weight loss.

The study had several limitations, which included:

Body weight was self-reported.
Weights were reported twice yearly; more frequent reporting might have yielded a different result.
Cancer-related symptoms that occurred at the same time as weight gain were not available.
The results might not be generalizable to different regions of the world.
The researchers collected data from 1978 to 2016. It might be less applicable to current practice.

The scientists also noted that participants were health professionals who could be more knowledgeable about cancer symptoms or have access to better healthcare.